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**A light particle solution to the cosmic lithium problem**

Andreas Goudelis, Maxim Pospelov, Josef Pradler

(Submitted on 29 Oct 2015 (v1), last revised 24 May 2016 (this version, v2))

We point out that the cosmological abundance of 7Li can be reduced down to observed values if during its formation Big Bang Nucleosynthesis is modified by the presence of light electrically neutral particles X that have substantial interactions with nucleons. We find that the lithium problem can be solved without affecting the precisely measured abundances of deuterium and helium if the following conditions are satisfied: the mass and lifetimes of such particles are bounded by 1.6MeV≤mX≤20MeV and few100s≲τX≲104s, and the abundance times the absorption cross section by either deuterium or 7Be are comparable to the Hubble rate, nXσabsv∼H, at the time of 7Be formation. We include X-initiated reactions into the primordial nucleosynthesis framework, observe that it leads to a substantial reduction of the freeze-out abundances of 7Li+7Be, and find specific model realizations of this scenario. Concentrating on the axion-like-particle case, X=a, we show that all these conditions can be satisifed if the coupling to d-quarks is in the range of f−1d∼TeV−1, which can be probed at intensity frontier experiments.

Comments: 5 pages, 4 figures; v2: minor improvements, matches published version

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)

Journal reference: Phys. Rev. Lett. 116, 211303 (2016)

DOI: http://arxiv.org/ct?url=http%3A%2F%2Fdx.doi.org%2F10%252E1103%2FPhysRevLett%252E116%252E211303&v=08290ee6

Cite as: arXiv:1510.08858 [hep-ph]

(or arXiv:1510.08858v2 [hep-ph] for this version)

any thoughts? what are the implications of such a particle to the SM and SUSY?

any connection with this?

**Evidence for a Protophobic Fifth Force from 8Be Nuclear Transitions**

Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo

(Submitted on 25 Apr 2016)

Recently a 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. The data are explained by a 17 MeV vector gauge boson X that is produced in the decay of an excited state to the ground state, 8Be∗→8BeX, and then decays through X→e+e−. The X boson mediates a fifth force with a characteristic range of 12 fm and has milli-charged couplings to up and down quarks and electrons, and a proton coupling that is suppressed relative to neutrons. The protophobic X boson may also alleviate the current 3.6σ discrepancy between the predicted and measured values of the muon's anomalous magnetic moment.

Comments: 6 pages, 2 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

Report number: UCI-TR-2016-09

Cite as: arXiv:1604.07411 [hep-ph]

Feng's paper, which comes later, does not reference nor cite the earlier paper by Goudelis et al, and does not state his proposed x boson would resolve the lithium 7 big bang overabundance problem.

Feng's xboson has right mass and lifetime and similar properties as proposed by Goudelis et al, to also reduce lithium 7 big bang overabundance problem.

Is it possible by Goudelis et al particle is the same particle as Feng's 17 mev Xboson?

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